-You will skip the step where you sub-cut the layer cake into 5" squares (since you're using charm packs, this step is already done!) You'll use your 4 print/color charm packs instead.
-You will skip cutting (16) 5" strips from your background fabric, since that is the step where you cut the background into charm packs. You'll use your 4 solid background charm packs instead.
Follow all the rest of the cutting and assembly instructions, and you're good to go!